Piston



Patented Jan. l2, 1943 arcane rrs'roN y Floyd F. Kishlina, Kenosha, Wis.,

Nash-Kelvinator Qorporaticn, VKenosha. a corporation oil Maryland assigner to Wist,

Application April n, ran, serian Na scatti (on scemisi 6 Claims.

This invention relates to pistons and hasparticular reference to a piston` for an internal combustion engine. i

It is an object of this invention to provide a piston which may have a closer t in the cylinder in which it is to operate than pistons used heretofore.

It is another object of this invention to provide a piston in which the transfer of heat from the face of the piston to the skirt of the piston. is largely prevented. 'w

It is another object of this invention to provide a divided piston in which the face or compression head of the piston is entirely separated from the skirt portion of the piston.

It is another object of this invention to provide means for mounting a compression head on a skirt in such a manneras lto prevent slap between the compression head and cylinder and to prevent the transfer of heat between the piston andthe skirt.

It is another object of this invention to provide a piston which retains the advantages of both cast iron and aluminum pistons while retaining few of the disadvantages of each.

Other objects and advantages of this invention will be apparent from a consideration of the following description and claims andthe attached drawings, of which there are two sheets, and in which- Figure 1 represents a longitudinal sectional view through a cylinder of an internal combustion engine showing a piston in operative position therein, the piston being shown partially in secion.

Figure 2 represents a horizontal sectional view taken along a plane indicated by the line 2-2 View similar to Figures l and 6 and showingJt` Figure l represents an elevational view of al' part of the compression head portion of a still y' further modified type of the piston and showing a piston ring in place thereon, the ring being shown in cross section; and

Figure li represents a sectional view taken along a plane indicated' by the line lI--ll in Figure l0 and looking in the direction o f the arrows. v

In the construction of internal combustion engines, it is desirable to have 'the pistons fit in the cylinders with as little clearance as possible in order tc prevent escape oi the combustion gases between the piston and the walls of the cylin-- der. It is lalso desirable to have the piston as light as possible to reduce the inertia forces which must be overcome each time the piston changes direction of movenrent in the cylinder. It is fur`- ther desirable to use a piston which will transmit as much heat as possible from the face of the piston to the cylinder-walls to reduce. the tendency for the engine to knock. n

In order to lighten the weight of the piston and increase the transfer of heat from the piston,

manufacturers have used pistons of cast aluminum but since aluminum has a high `co-eilicierit of expansion relative to the co-efcient of exl pansion of the usual cast iron cylinder blocks, it has been necessary to use rather large clearances between the piston and the cylinder when the Y parts are cold. This caused what is known as in 'Figure 1 and looking in the direction of the arrows; A

Figure 3 represents a side elevational view of the compression, head portion of the piston shown in Figures 1 and 2;

Figure 4 represents a plan view'of the skirt portion of the piston shown in Figures 1 and 2;

Figure 5 represents a sectional view taken along a plane indicated =by the line 5 5 in Figure 4 yand looking in the direction of the arrows;

piston slap and results in a noisy engine. To compensate for this undesirable characteristic of aluminum pistons, they have been provided with a compression head portion and a skirt portieri. The compression head portion is made with tively large clearance in thecylinder to provide for the expansion of the head and the skirt portion is made with relatively small clearance to provide an accurate. guide for the piston. To t insulate the skirt portion so far as possible from the head portion in order to reduce thexpansion of the skirt portion, the head is divided so far as possible from the skirt` The skirt is also split in some cases to further provide for expansion. This invention provides a piston with a compres,-

sion head portion which is entirely separate from` the skirt portion and thus prevents the transfer of heat from the head portion to the skirt portion to a large extent. With this construction, it is possible to construct the compression head of aluminum for low knock characteristics and to construct the skirt of cast iron to obtain a close flt between the guiding portion of the piston and the cylinder.

In the drawings, in which similar reference characters havebeen used to designate similar parts, there is illustrated a cylinder 26 of an internal combustionmotor provided with a water jacket 22. Reciprocably mounted in the cylinder 20 is a piston generally indicated at 24 which is connected through a wrist pin 26 to a connecting rod 28. The connecting rod is provided with a lower bearing portion 30 by means of which the connecting rod'may be attached to the usual crank shaft (not shown).

More specifically, the piston 24 consists of a compression head portion 32 having grooves in itsy side wall in which are mounted the compression rings 36 and an oil ring 38. Positioned below the compression head 32 of the piston is a skirt portion 40 which has a continuous cylindrical surface in contact with the walls of the cylinder 20 and which may be made to t within the cylinder with very small clearance for reasons which will appear presently.

The compression head portion 32 is made to fit within the cylinder 26 with relatively large clearance and is hollow to reduce its weight. I'he compression head may be provided with internal ribs 42 to reinforce the face of the piston and brace the face with respect to the side walls of the compression head. 1

VAs is most clearly illustrated in Figures 2 and 3, the compression head 32 of the piston 24 is provided with a pair of arms 44 which extend downwardly below the sidewalls oi the compression head portion and which are positioned in spaced relationship along a diameter of the compression head. The arms 44 are provided with bosses 46 which extend radially inwardly toward each other and which are apertured'along with the arms 44 as at 48 to receive the wrist pin 26. It will be noted that thev outer faces 50 of the arms 44 are spaced inwardly from the circumference of the compression head and are vertical and parallel. The inner faces 52 of the bosses 46 are also vertical and parallel. The compression head is preferably formed of east aluminum in much the same manner in which present day pistons are manufactured.- a

The skirt portion 40 .of the piston 24 is most clearly illustrated in Figures 2, 4 and 5 and consists of a circular cylinder having annular ribs 54 extending around the inside surface thereof lfor the purpose of strengthening the cross head. Formed on the inner surface of theskirt 46 at opposite ends 'of a diameter of the skirt are a pair of bosses 56 which, together with the side wall of the skirt, define apertures 56 designed to receive the ends ofthe wristpin 2.6. Annul'ar ribs 60 are formed around the inner edges of the bosses 56 to strengthen them and the annular ribs 54 may on the compression head 32. The skirt 46 is prei'- erably made of cast iron.

When the piston 24 is assembled, the ends ofthe wrist pin 26 are journaled in the apertures 58 of thebosses 56 formed on the skirt 46 while the arms 44 and bosses 46 of the compression head 75 32 are journaled on the wrist pin Just within the bosses 56 of the skirt. The connecting rod 26 is attached to the wrist pin 26 between the faces 62 of the compression head 32 and is arranged to be spaced slightly therefrom. The connecting rod is shown to be fixed relative to the wrist pin 26 by a locking pin 64 but may be allowed .to rotate relative to the wrist pin if so desired.

It shouldv thus be apparent that .there is no connection between the compression head 32 and arms 44 to the wrist pin 26 and .then .to the skirt or through the walls of the cylinder to the skirt. Since the walls are cooled by the water jacket 22 and since the arms 44 oi'. the compression head have a relatively small cross section for the transfer of heat, the skirt 40 will operate at a considerably lower temperature than the compression head and as a result may be manufactured to ilt within the cylinder with a relatively small clearance. The fact that the skirt is made of cast iron and will expand at the same rate as the cylinder allows the clearance to be further reduced. This results in a smoother operating engine and in less distortion of the ring grooves due to the expansion of the piston.

'I'he compression head 32 may be designed solely to. take the compression thrust of the burning gases and to prevent their escape between the compression head andV the walls of the cylinder without consideration of problems relating to the guiding of the compression head in the cylinder, these problems already being taken care of by the construction of the skirt and wrist pin.

The construction thus just described has been found to have one disadvantage in that the wristl pin 26 oscillates relative to the compression head 32 and the arms 44 as the bearing portion 30 of the connecting rod is carried around by the crank shaft. Suflicient friction may be developed between the surface of the wrist pin 26 and the surface of the apertures 48 in the arms 44 and bosses 46 to tend to rotate the compression head about the wrist pin as an axis. With the liberal clearances provided between the compression head and the cylinder walls, this rotation has been found to produce a knocking or slapping noise in the engine. To remedy this situation, various modified forms of mounting the compression head relative to the skirt are illustrated in Figures 6 through 11 which will be described presently. In so far as possible, similar p'arts of each modified form 4of the piston are numbered with reference characters in the same order-but in separate hundreds in order to indicate the relationship between the various modiications. Where parts are unchanged, the same reference characters are used.

Figures 6 and 7 illustrate a piston in which the compression head |32 is shaped as by machining to have an annular shoulder |33 formed therearound just underneath the grooves 34 which l When the lccmpressipn head |32 tends to rotate in the cylinder 20 due to friction between the wrist pin 26 and the arms 44, this motion is resisted 'and cushioned by flexing of the fingers |31 of the annular spring |35. In other respects the construction of the piston is the same as that shown in Figures 1 of the spring v |35 prevents the compression head from slapping against the cylinder walls and the fingers |31 will not transmit enough heat to the skirt to lose the benefits of the divided piston.

In the modification shown in Figures 8 and 9, the apertures 258 and 248 in the skirt 248 and compression head 232 respectively are slightly larger than the corresponding apertures 58 and 48 shown in the other modifications o f the invention and are arranged to receive sleeves 239 of anti-friction material. These sleeves may be pressed into the apertures 258 in the skirt 240 so that they will not rotate relative to the skirt or the compression head 232. The wrist pin will then rotate within the sleeves 239 relative to the skirt 248 and compression head 232 as the pin is oscillated by the connecting rod 28 and will have no frictional contact with the compression head tending to rotate the head in the cylinder. The compression head 232 is thus not subjected to any rotative forces and hence will not knock against the side of the cylinderv 20. .Figures 8 and 9 illustrate the compression head 232 as also being provided with an annular spring |35 the same as that shown in Figures 6 and '1; however, this spring may be omitted if desired since the sleeve 238 removes all tendency for the compression head to knock in the cylinder.

In the modified form of the invention illustrated in Figures 10 and 1l, the compression head 332 is provided with a special ring groove 334 at the bottom thereof in which is positioned an oil ring 338 which is urged, radially outwardly bya piston ring expander spring 34| to engage the walls of the cylinder. The particular type of piston ring expander is unimportant to thel invention since any type of spring of proper strength will serve the function. The particular form of expander shown consists of a spring having wavy contour and retained behind the piston ring 338 by engagement with the shoulders 343 (see Figure 1l) formed on the ends of the piston ring.

With the piston ring expander 34| in position, any force tending to rotate the compression head 332 relative to the cylinder must first compress the expander 34| before the piston strikes the wall of the cylinder; thus the piston ring expander acts to prevent thecompression head from knocking against the wall of the cylinder.

Any one of the features illustrated in Figures 6 through 11 or any combination of them may be used to prevent piston slap depending upon the amount of money desired to be spent on the piston since each feature will naturally entail some expense in manufacture.

While I have described my invention in some detail, I intend this description to be an example only and not as a limitation of my invention, to which I make the following claims.

through 5. Theaction I claim: 1. A piston for an internal combustion engine `comprising a-cylindrical compression head mem- `comprising a cylindrical skirt member, a wrist pin journaled in said skirt member, a cylindrical compression head pivotally supported upon said pin in spaced relationship with said skirt member so as to permit relative rocking movement of said members about said pin, and spring means extending between said skirt and compression head member arranged to restrain rotation of said compression head member about said pin relative to said skirt member.

,3. A piston for an internal combustion engine comprising a compression head having a top sur'- face and cylindrical side walls, said side walls 'having an annular shoulder formed along the bottom edge thereof and spaced radially inwardly from the outer surface thereof, a pair of arms extending downwardly from said side walls and spaced radially inwardly therefrom, a cylindrical skirt positioned below said annular shoulder on said compression head and spaced therefrom, a wrist pin journaled in said arms and said skirt, and spring means positioned between the top of said skirt and said annular shoulder on said compression head.

4. A piston for an internal combustion engine comprising a compression head having a top surface and cylindrical side walls, said side walls having an annular shoulder formed along the bottom edge thereof and spaced radially inwardly from the -ou'ter surface thereof, a pair of arms extending downwardly from said side walls and spaced radially inwardly therefrom, a cylindrical skirt positioned below said annular shoulder on said compression head and spaced therefrom, a wrist pin journaled in said arms and said skirt, and spring means positioned between the top of said skirt and said annular shoulder on said com pression head, said spring means being cut away to contact said skirt at spaced intervals.

5. A piston comprising a compression head member, a skirt member, a wrist pin, said members being journaled upon said pin and spaced from each other, and means for preventing said members from tilting relative to each other about the axis of said pin.

6. A piston comprising a compression head member, a skirt member, a wrist pin, said members being supported upon said pin and spaced from each other, and spring means carried by one of said members operable to restrain rotation of said one member relative to the other of said members.

- FLOYD F. KISHLINE.

'Patent No. 2,508,178.

column, line 57,

CERTIFICATE 0F CORREO TION.

January l2, 191;.5..

FLOYD F. KISHL'INE.

It is hereby certified that error appers 1p the printed specification of the above numbered patent reqiring Acorrection as follows g' Page 2 first line 55, claim 5, forfmeans for prevanting' -read sprig means for restraining andv thgt the 'sam Letters Patent lshtuld be read with this correction therein that the same may confonn to the record of the case in the Patent Office. Y t I signed and lsmiled this 2nd day of naz-ch, A. D. 1915.

. u Henry Van Arsdale, (5981)' Acting Commissioner of Patents.

for 'cross heed read --skirt-f; page 5, seoond column. 

